It has recently been proposed to provide a rocking chair in which the member supporting the chair from the chair base is a flexible plastic sheet means which is connected at one end to the chair and at the opposite end to the chair base. This flexible sheet means may be in the form of a fiber reinforced plastic material, the reinforcing fibers preferably consisting of continuous glass filaments. It has been found that this sheet material provides a smooth rocking action. Furthermore, it is extremely inexpensive to manufacture a chair employing such a sheet of flexible plastic material as the chair seat supporting means.
Several patents have issued in recent years directed to such chairs. One such patent is the Pentzien U.S. Pat. No. 4,119,343 in which the flexible sheet means are disposed in various manners. In one case, the sheet means is disposed at an angle of almost 45.degree.. In another, it is disposed vertically.
Another patent somewhat similar to the Pentzien patent is the Ward U.S. Pat. No. 4,141,530. This patent likewise shows various embodiments, in some of which the flexible strip is disposed at an angle of nearly 45.degree. and another in which the flexible strip is disposed vertically.
There are several problems in connection with constructions such as shown in the Ward and Pentzien patents. If the strip is disposed vertically, the chair tends to be unstable about its normal position. In other words, very little rocking force is required to cause the chair to move either forward or back. On the other hand, if the flexible strip is disposed at an angle such as 45.degree., there is a very substantial vertical bending force applied to the strip, placing it under very large bending force.
Another drawback to the arrangements of the Pentzien and Ward patents is that there is no effective stop means to limit the flexure of the strip. It is highly desirable with a flexible plastic spring member such as employed in this type of chair for there to be some means for limiting the rocking motion in both the forward and rearward directions.
In the pending application of Donald L. Bottemiller and John K. Miles, Ser. No. 164,824, filed June 30, 1980, which has matured into U.S. Pat. No. 4,371,142, dated Feb. 1, 1983. there is disclosed a chair of the general type employing a flexible plastic spring member for supporting the chair seat from the chair base in which the flexible strip is inclined rearwardly at a slight angle. The angle with respect to the vertical is sufficiently small that the force applied to the strip is basically a vertical force. At the same time, the angle of inclination is sufficiently large that a slight bias is applied to the strip eliminating the unstable condition which exists when the strip is vertical. In addition, the structure shown in the aforesaid application of Donald L. Bottemiller and John Miles provides a stop means which effectively limits the rearward movement of the chair, thus limiting the rearward flexure.